Not to put you on the defense, because I'm sure that's how you will take it. So I may as well apologize now. Sorry, but WHY would anyone want to expose puppies to unnecessary radiation? That just makes me so sad for them. Can't you just wait until Nature says it's time, and see how many you get? X-rays are not needed. Dogs have been doing this for years without intervention. Unless you're anxious to see how much money you're going to make, there is absolutely no reason to X-ray anything. People wonder how their "champion bloodlines" could produce a pup with defects. Well, gee... ever look into the effects of RADIATION? There's a reason why they don't X-ray pregnant humans. Did you think it would be any different for animals? If your vet said it's safe, they're thinking of their wallet, and not your puppies. Amazing what the selfish drive for money will make people do.
*stepping off my soapbox* I do pray you have a healthy litter of puppies that all find great homes. Sorry if I sound rude. I just love puppies, that's all.